The plasma ablation by means of HF power, which is guided to an electrode, for removing plaque in blood vessels is known from WO 2011/055369. The corresponding instrument is inserted into the blood vessel and creates a HF spark at its distal end, which acts on plaque or also on other biological material, such as blood. The created light is supplied to an optical spectrometer, which, by means of the presence or absence of the typical phosphor spectral line, provides information, whether living cells or plaque are dissolved by the spark.
On principle, it is thus possible for the user to concentrate the surgical action to certain biological structures, here the plaque, by means of corresponding machine support, and to preserve other tissue.